big one

big one

1. Something very important that one has been working or striving to achieve or win. Used after "the." OK, boys, this is the big one—the regional championships. Today we put our months of hard work to the test. This deal is the big one. Our company's entire future depends on us securing it.
2. Something extremely catastrophic or devastating. Used after "the." Analysts are warning that the destruction caused by the recent earthquakes would pale in comparison to the big one that could be coming down the line. It was only a minor heart attack, thank God, but the doctors say he might not survive if he's ever struck by the big one.
3. slang A unit of one thousand dollars. Used in plural constructions. The landscaper said it would cost five big ones to replace the sprinkler system. I spent 30 big ones on this damned car, and it's given me nothing but trouble since the day I bought it.
See also: big, one
Farlex Dictionary of Idioms.

the big one

n. a serious heart attack, possibly fatal, especially if anticipated or dreaded. He survived the big one but kept on smoking.
See also: big, one
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • (one) could use (something)
  • cooking for one
  • drive (one) out of office
  • force (one) out of office
  • force out of office
  • give (one) (one's) head
  • give head
  • give somebody their head
  • give someone their head
  • 1FTR
References in classic literature
Big business begun; an' big business means big business men; an' every big business man means thousands of little men without any business at all except to work for the big ones. They're the losers, don't you see?
"With all my heart," said the barber; and not caring to tire himself with reading more books of chivalry, he told the housekeeper to take all the big ones and throw them into the yard.
She must have two footmen behind her carriage, and very big ones. That was her taste.
"She will see ours capitally, but miss the big ones on the hill, unless papa has forgotten all about them," added Steve, cutting short the harangue Mac had begun upon the festivals of the ancients.
Uy said the Philippines is prone to earthquake and has been preparing for the 'Big One,' or a 7.2-magnitude earthquake.
Help raise money for the cancer charity with one of the sponsored walks, including The Banchory Big One, at 15 miles - participants must be aged 12 or over - and The Milton Mini, at three miles.
This could help explain public fear of the 'Big One," the (https://www.ibtimes.com/mega-earthquake-chile-long-overdue-big-one-1657962) mega  earthquake that could cause catastrophic damages.
Specifically, Moreno asked Navy and Army reservists to assist Manila during calamities, particularly the so-called Big One - referring to quake.
RELATED: LGUs urged to develop own ecozones "They also recommended decongestion of Metro Manila by reducing its population density and incentivizing the economic activities outside of the region, as well as to require all agencies to submit their public service continuity plans should 'The Big One' occur," he said in a statement.
The government experience in handling the response on the 6.2 magnitude quake that left destruction in Pampanga will be used as an input for the preparations for the so-called 'Big One' that is feared to strike Metro Manila and nearby areas anytime.
'The Big One', which has been held in Farnborough, Hampshire for around 20 years, will hold a second edition of the show at the NAEC Stoneleigh near Kenilworth.
PAUL Scholes has summed up United's rivalry with Liverpool by insisting the clash is still 'the big one' despite the emergence of City.
British Red Cross PS5 Many thanks to Saints Jude, Anthony, Martin de Pores and Our Lady for a small miracle (but a big one for me).
The club's commercial director Mick Hogan revealed their plan to continue growing the 'Big One' over the next two seasons.